The invention concerns a heavy vehicle for breaking up ground provided with retracting and steering rear wheels.
It is known that for breaking up ground, specific heavy vehicles are used equipped with wheels or tracks depending on how they are implemented and provided with equipment suited to breaking up the actual ground.
Scarifiers are, for instance, known for this purpose that are heavy vehicles used to break up the bituminous surface covering road courses.
A scarifier fundamentally consists of a frame made of heavy-duty metal bodywork, provided with a ripper drum that is set against the ground to be broken up and is supported by a horizontal shaft around which it is rotated.
The frame, which is shaped to provide a driver's cab where the operator sits, is in turn supported by a pair of front drive wheels or tracks and a pair of rear wheels or tracks, either with drive or free, the latter being located next to the ripper drum. Traction systems, housed in an engine compartment formed out of the frame, set the ripper drum in rotation to break up the ground and the wheels or tracks to move the machine.
The rear wheels or tracks are connected to a sole-plate supported by a hydraulic cylinder that allows a vertical movement to adjust the depth the ripper drum penetrates into the ground while an articulation fixed to the frame and connected to the actual sole-plate allows one or both wheels or tracks to be set in a retracted position inside the frame.
The rear wheels or tracks when extracted from the frame, allow better weight distribution primarily during the machine's use, while the possibility of at least one wheel or one track retracting under the frame, allows the machine to be used for digging right up to the wall of the work area.
What's more the position of one or more of the rear wheels or tracks when retracted into the side of the machine, allows to reduce the machine's overall dimensions and aid road transport when it is moved from one work site to another. Known machines equipped with one or both rear wheels or tracks retractable are extended manually and therefore by operations that are awkward for the operator since, to carry them out he has to get down from the machine and go to one or both of its sides to shift the wheels or tracks.
As an alternative to manual retraction, the depositee of this invention has filed an Italian patent application having protocol number V198U000098 which describes a heavy vehicle for breaking up ground in which the changeover of one or both rear wheels or tracks from extracted to retracted into the frame and vice versa, as well as locking them in their final position, is achieved automatically by controls inside the driver's cab.
One limitation shown by the machine described in the aforementioned patent is that when the rear wheels or tracks are set in their retracted position inside the frame, when turning they scrape the ground with considerable resistance. This problem is particularly accentuated when the machine is fitted with tracks rather than wheels, because in this case the resistance while turning is even higher because of the greater surface area in contact with the ground.